The present invention relates to hypodermic syringes and, in particular, to a safety syringe to prevent accidental needle pricks and reuse of a hypodermic syringe.
Syringes are often used for administering medication to patients suffering from infectious diseases. Numerous cases have been reported in which doctors, nurses, or other medical personnel have been infected by accidental needle pricks. The seriousness of the problem has become more acute in light of the recent spread of Acquired Immunodeficiency Syndrome (AIDS). Accordingly, it is of utmost importance that extreme care be exercised in the handling and disposal of hypodermic syringes after use to prevent the accidental transmission of the HIV virus, as well as other infectious diseases.
The spread of the HIV virus has often been attributed to the sharing of contaminated needles by illicit drug addicts. While most hypodermic needles are intended to be disposable, they are frequently reused and shared. Often times, the drug users obtain hypodermic syringes by stealing used syringes from hospitals and other medical facilities. Such needles may already be contaminated with the HIV virus. However, even when "clean" needles are obtained, it may still be infected with the HIV virus by one drug user and then transmitted to another drug user with whom the needle is shared.
In view of the seriousness of the AIDS epidemic, there is a need for a safety syringe which will help prevent accidental needle pricks and discourage illegal drug users from reusing or sharing needles. In the past, various types of guards or shielding devices have been devised for hypodermic needles to prevent accidental needle pricks. Typically, the guard is slidably mounted on the syringe barrel and is moveable from an extended position in which the protective shield overlies the needle and a retracted position in which the shield is retracted to expose the needle. These guards may include a latching mechanism for securing the guard in a particular position with respect to the needle and syringe. Patents which disclose an axially slidable shield or guard include U.S. Pat. Nos. 4,127,910 to Tallon et al; 5,120,309 to Watts; 4,801,295 to Spencer; and 3,890,971 to Leeson et al.
These prior art protective shields are generally suitable for protecting medical personnel from accidental needle pricks. These known devices satisfy many of the functional requirements of a protective shield. However, these prior art devices suffer from several drawbacks. One drawback is the complexity of the shield mechanism. Many of the prior art shields have complicated structures with multiple parts. The complexity of these devices makes them relatively costly to produce.
Another disadvantage with prior art safety syringes is that they do not effectively prevent reuse of a contaminated needle. Most of the prior art devices do not include an irreversible locking mechanism to secure the protective shield after use. As a result, it is possible to inadvertently reuse a needle which may have been contaminated. Even those protective devices which have irreversible locking mechanisms on the protective shield can be easily defeated by persons wanting to acquire such needles for illegal use. In most instances, the protective shield can be removed without destroying the function of the hypodermic syringe.